The present invention relates to the use of ion beams as a tool to study radiation damage to materials. A beam of heavy ions can produce radiation damage at a rate of several orders of magnitude greater than in a reactor thus allowing rapid experiments to determine the probable reaction of a given material to the radiation flux associated with a nuclear reactor. It is known to use one, or several ion beams of different energies which converge on a sample mounted to an electron microscope to observe the reaction of a material to radiation damage. A neutron flux can be simulated by high energy large ions such as aluminum or iron which cause dislocations in the crystal structure of metals or other materials. Often the heavy ions which simulate the neutron damage are combined with a second lower energy beam of ionized hydrogen or helium which simulates the formation of helium and hydrogen gas from protons or alpha particles. The combination of the two beams: a high energy beam when producing crystal defects or dislocations, and a low-energy beam which deposits ions which form the gases which can fill or create voids in the crystal structure producing characteristic swelling encountered in reactor materials over long periods of time.
In one known arrangement, a high energy beam and a low energy beam have been combined by using magnetic lenses so that the single combined beam deposits high energy ions and low-energy gas forming ions on a substrate under test within an electron microscope combining the elements of radiation damage, crystal dislocations and gas formation. However, magnetic lenses are energy use intensive and may affect the electrons used in the electron microscope. Further, a steering magnet applies a force which is proportional to the velocity and the velocity is inversely proportional to mass. Thus for a given beam energy, different isotopes of the same energy will not be bent by the same amount.
What is needed is a device for combining two or more ion beams of dramatically different energies using electrostatic lenses.